Method of generating a drive signal for a loudspeaker arranged in a motor vehicle, an exhaust system for an engine and a sound system for a passenger cell

Abstract

A method of generating a drive signal for a loudspeaker in an exhaust system of an engine of a vehicle or inside or outside a passenger cell includes providing a predetermined source signal for a desired additional sound in a time domain comprising a plurality of signal components of different frequencies; analyzing the source signal based on a phase of the source signal and/or a phase of at least one oscillation in the source signal; identifying a phase of engine noise and/or a phase of at least one oscillation existing in engine noise; shifting the phases of the source signal and/or the oscillation existing in the source signal based on phases identified in engine noise and/or in oscillation existing in engine noise, the relationship of phases of individual oscillations of the source signal among each other being preserved; and generating the drive signal based on the phase-shifted source signal.

The invention claimed is: 
     
       1. A method of generating a drive signal for a loudspeaker arranged in a motor vehicle, in particular in an exhaust system of the engine of the vehicle or inside or outside a passenger cell, comprising the following steps:
 (a) providing a predetermined source signal for a desired additional sound in a time domain, the source signal comprising a plurality of signal components of different frequencies, 
 (b) analyzing the source signal with respect to a phase of the source signal and/or a phase of at least one oscillation existing in the source signal, 
 (c) identifying a phase of the engine noise and/or a phase of at least one oscillation existing in the engine noise, 
 (d) shifting the phase of the source signal and/or the phase of the at least one oscillation existing in the source signal as a function of the phase as identified of the engine noise and/or of the phase as identified of the at least one oscillation existing in the engine noise to provide a phase-shifted source signal, a relationship of the phases of the individual oscillations of the source signal among each other being preserved, and 
 (e) generating the drive signal on the basis of the phase-shifted source signal. 
 
     
     
       2. The method according to  claim 1 , wherein the oscillation existing in the engine noise and/or in the source signal is a harmonic oscillation of one of a plurality of engine orders. 
     
     
       3. The method according to  claim 2 , wherein the oscillation existing in the engine noise and/or in the source signal is a harmonic oscillation of a 0.5th engine order. 
     
     
       4. The method according to  claim 2 , wherein for shifting the phases, a preferred engine order is determined, the phase of the oscillation, corresponding to this preferred engine order, of the source signal and the phase of the oscillation, corresponding to this preferred engine order, of the engine noise are either adjusted to each other or equated. 
     
     
       5. The method according to  claim 4 , wherein the phase of an oscillation, corresponding to one and/or the preferred engine order, of the source signal and the phase of the oscillation, corresponding to this one and/or the preferred engine order, of the engine noise are offset by 180 degrees relative to each other. 
     
     
       6. The method according to  claim 1 , wherein the shifting of the phase of the source signal is carried out in a frequency domain. 
     
     
       7. The method according to  claim 1 , wherein the analyzing of the source signal is carried out by a transformation to a frequency domain. 
     
     
       8. The method according to  claim 7 , wherein the analyzing of the source signal is carried out by one of a Fourier transform or a fast Fourier transform (FFT). 
     
     
       9. The method according to  claim 1 , wherein the phase of the engine noise and/or the phase of at least one oscillation existing in the engine noise is identified by a transformation of the engine noise to a frequency domain. 
     
     
       10. The method according to  claim 9 , wherein, the phase of the engine noise and/or the phase of at least one oscillation existing in the engine noise is identified by at least one of a Fourier transform or a fast Fourier transform (FFT) and is based on sensor data. 
     
     
       11. The method according to  claim 1 , wherein the source signal comprises signal components that include a signal picked up before. 
     
     
       12. The method according to  claim 1 , wherein the source signal comprises synthetically generated signal components. 
     
     
       13. The method according to  claim 12 , wherein the source signal comprises synthetically generated signal components in a form of sinusoidal tones. 
     
     
       14. The method according to  claim 1 , wherein a level of an oscillation existing in the source signal is reduced if a frequency of this oscillation is close to a frequency of an undesirable resonance. 
     
     
       15. The method according to  claim 1 , wherein the source signal has a root mean square value of a voltage of at least 50% of a maximum voltage of the loudspeaker. 
     
     
       16. An exhaust system for an engine, in particular of a motor vehicle, comprising:
 a loudspeaker and a controller, the controller being configured to
 provide a predetermined source signal for a desired additional sound in a time domain, the source signal comprising a plurality of signal components of different frequencies, 
 analyze the source signal with respect to a phase of the source signal and/or a phase of at least one oscillation existing in the source signal, 
 identify a phase of the engine noise and/or a phase of at least one oscillation existing in the engine noise, 
 shift the phase of the source signal and/or the phase of the at least one oscillation existing in the source signal as a function of the phase as identified of the engine noise and/or of the phase as identified of the at least one oscillation existing in the engine noise to provide a phase-shifted source signal, a relationship of the phases of the individual oscillations of the source signal among each other being preserved, and 
 generate the drive signal on the basis of the phase-shifted source signal; and 
 
 wherein the controller drives the loudspeaker by the drive signal. 
 
     
     
       17. The exhaust system according to  claim 16 , including an exhaust branch and a microphone, the loudspeaker being in fluidic contact with the exhaust branch at a contact point, and the microphone being arranged upstream or downstream of the contact point. 
     
     
       18. A sound system of a motor vehicle, in particular for a passenger cell, comprising:
 at least one loudspeaker and a controller, the controller being configured to
 provide a predetermined source signal for a desired additional sound in a time domain, the source signal comprising a plurality of signal components of different frequencies, 
 analyze the source signal with respect to a phase of the source signal and/or a phase of at least one oscillation existing in the source signal, 
 identify a phase of the engine noise and/or a phase of at least one oscillation existing in the engine noise, 
 shift the phase of the source signal and/or the phase of the at least one oscillation existing in the source signal as a function of the phase as identified of the engine noise and/or of the phase as identified of the at least one oscillation existing in the engine noise to provide a phase-shifted source signal, a relationship of the phases of the individual oscillations of the source signal among each other being preserved, and 
 generate the drive signal on the basis of the phase-shifted source signal; and 
 
 the controller to drive the loudspeaker by the drive signal. 
 
     
     
       19. The sound system according to  claim 18 , wherein the loudspeaker is arranged inside or outside the passenger cell. 
     
     
       20. The sound system according to  claim 19 , wherein the sound system is part of a stereo and/or entertainment system of the motor vehicle.